1. Field of the Invention
The present invention relates to a laser beam irradiation apparatus (an apparatus including a laser oscillator and an optical system for guiding laser light to a subject to be irradiated) and a laser light irradiation method. Further, the present invention also relates to a method for manufacturing a semiconductor device, including a step of the aforementioned laser light irradiation method. The present invention relates to a method for manufacturing a display device using a printing method.
2. Description of the Related Art
In recent years, growth in size and reduction in cost of liquid crystal televisions and plasma televisions have proceeded. Accordingly, liquid crystal televisions and plasma televisions have been capturing the television market at higher rates than CRTs (tube televisions). As a background against which reduction in cost of liquid crystal televisions and plasma televisions have proceeded, a progress in technology for manufacturing a thin film transistor (hereinafter referred to as a TFT) on a glass substrate is conceivable. In particular, productivity in the case of large substrates is remarkably increased and the amount (the number) of products obtained from one substrate is increased; therefore, prime cost is reduced and production is increased, which leads to reduction in cost of products.
Thin film transistors (hereinafter also referred to as TFTs) and an electronic circuit using a thin film transistor are manufactured by stacking thin films such as semiconductor films, insulating films, or conductive films over a substrate and forming a predetermined pattern as appropriate by a photolithography technique. A photolithography technique is a technique for transferring a pattern onto a substrate by utilizing light and a photomask. The pattern is formed on the photomask, by forming a pattern of a circuit or the like using a light-blocking material on a surface of a transparent planar plate, and it has been generally used in manufacturing processes for a semiconductor integrated circuit and the like. Then, an insulating film, a semiconductor film, a metal film, or the like is partially etched to be removed by using as a mask a pattern transferred to a substrate with the use of photolithography technique, so that the contact hole can be formed in a desired position.
For example, in the case of obtaining a contact hole having a desired shape by using photolithography technique, first, a photosensitizing agent such as a resist material is applied to a thin film on the substrate. Next, the substrate to which the photosensitizing agent is applied is irradiated with light having a wavelength, by which the photosensitizing agent is sensitized, through a photomask on which a desired pattern is formed in advance. Then, the pattern formed on the photomask is transferred to the photosensitizing agent (patterning process). From the substrate on which the pattern is formed, a portion of the photosensitizing agent, in which patterning is not performed, is removed and a portion of the photosensitizing agent, in which patterning is performed, is left as it is by appling developer (developing treatment). Thereafter, from the substrate, a portion of the thin film, over which a resist is not left, is removed by a dry etching method or a wet etching method (etching treatment) and at last, the left photosensitizing agent is removed by remover (removing treatment). Accordingly, the contact hole having a desired shape can be formed.
A conventional manufacturing process using a photolithography technique requires multiple steps of at least exposure, development, baking, removing, and the like. Therefore, as the number of the photolithography steps increases, the manufacturing cost inevitably increases. In order to solve this problem, attempts have been made to manufacture TFTs using a smaller number of photolithography steps (for example, see Patent Document 1: Japanese Published Patent Application No. 2000-133636). In Patent Document 1, after a resist mask formed by photolithography steps is used once, its volume expands and then is used again as a resist mask having a different shape.